This document provides information on 5 species of small, drought-tolerant trees suitable for landscapes in Maine: Miyabe Maple, Three-flower Maple, Eastern Redbud, Amur Maackia, and Sargent Cherry. It describes the origin, characteristics, cultural requirements and ornamental features of each tree species. The document is intended to introduce potentially new landscape plants that are cold hardy and meet criteria for exceptional small trees.

1. ISSN 1070–1494
Drought-tolerant Small Trees for
Drought-tolerant Small Trees for
Maine Landscapes
Maine Landscapes
Reeser C. Manley
Reeser C. Manley
Bulletin 849 September 2003
MAINE AGRICULTURAL AND FOREST EXPERIMENT STATION
The University of Maine
The University of Maine

2. Drought-tolerant Small Trees for
Maine Landscapes
Reeser C. Manley
Assistant Professor of Horticulture
Department of Plant, Soil and Environmental Sciences
The University of Maine
Orono, ME 04469

3. ACKNOWLEDGMENTS
The image on the cover is a picture of a flowering Maackia
amurensis from the Lyle E. Littlefield Ornamentals Trial Garden at
The University of Maine. The drawings used throughout this
bulletin were drawn by Margery Read, a Master Gardener in The
University of Maine Cooperative Extension’s Master Gardener
program.
The Maine Agricultural and Forest Experiment Station pro-
vides equal program opportunities without regard to race, age, sex
or preference, creed, national origin, or disability.

4. 4 MAFES Bulletin 849
INTRODUCTION
There is a great deal of interest these days in the smaller
deciduous trees, plants that mature to 30 feet or less in height. Too
small to be considered shade trees, the best of these “courtyard” or
“patio” trees should have characteristics that make them ornamen-
tal features of the small landscape throughout the year. The ideal
representative of this group would combine seasonal flower display
with attractive foliage, rich autumn leaf color, interesting bark
character, attractive branching habit, and resistance to insects and
diseases. In addition, there would no messy fruit to clean up. From
a production point of view this plant must be easy to propagate.
And, of course, for northern regions the likely candidate must also
have extreme cold hardiness. Finally, non-native plants selected for
use in managed landscapes should not be invasive. We don’t ask for
much!
Actually there are a few tree species of small stature that come
close to meeting these demanding requirements. For the past five
years I have been growing several species of small trees in a
replicated trial at The University of Maine, Orono. This publica-
tion, the first published results from this effort, describes five
species that have proven to be reliably cold hardy in Orono (USDA
Zone 5a) and that meet many, if not all, of the criteria for excep-
tional landscape trees. In addition, these five species are currently
uncommon in Maine landscapes and thus represent potentially new
products and new opportunities for the Maine landscape and
nursery industries.
THE TREES
Tables 1 and 2 give basic information and cultural require-
ments, respectively, for the five species. The following descriptions
are taken from my lecture notes for the woody landscape plants
courses at The University of Maine.
Acer miyabei, Miyabe Maple
Discovery of this rare tree occurred by accident. In the nine-
teenth century, Professor C. S. Sargent of the Arnold Arboretum,
while waiting for a train in Yezo, Japan, strayed from the station
and into a grove of trees on the border of a stream where he found
A. miyabei in fruit. He later obtained seed from the trees, leading
to the commercial introduction of A. miyabei to the U.S. in 1892.
My first encounter with Acer miyabei (Miyabe Maple) was a
single tree growing in a courtyard at Smith College Arboretum in

5. MAFES Bulletin 849
Table 1. Species of small flowering trees evaluated in this study.
USDA Mature Mature
Botanical Name Common Name Native Range Hardiness Height Width Growth Rate
Acer miyabei Miyabe Maple Northern Japan Zone 4 20 to 25’ 15 to 20’ Slow to medium
Acer triflorum Three-flower Maple Manchuria and Korea Zone 3B 15 to 25’ 15 to 25’ Slow to medium
Cercis canadensis Eastern Redbud Southeast and central U.S. Zone 4B 20 to 30’ 15 to 25’ fast
Maackia amurensis Amur Maackia Manchuria Zone 3 20 to 35’ 15 to 25’ slow
Prunus sargentii Sargent Cherry Japan Zone 5 25 to 40’ 25 to 40’ fast
5

6. 6
Table 2. Cultural requirements for the five species of small flowering trees.
Botanical Light Drought Salt Pests and
Name Requirement Soil Tolerance Tolerance Tolerance Diseases Propagation
Acer miyabei Full sun Adapts to a broad High High Excellent Softwood cuttings, bud-
range of soil types. resistance ing or tissue culture
Acer triflorum Full sun to Tolerant of clay, Moderate Moderate Excellent By seed, but with very
partial shade loam or sand; prefers resistance low rates of germination;
acid or slightly alkaline can be grafted onto
and well-drained soils. other trifoliate maple
rootstock.
Cercis canadensis Full sun in Adapts to a broad High Poor Usually not By seed
northern range of soil types. bothered by
landscapes; Prefers well-drained, insect pests.
partial shade in acidic or slightly Susceptible to
the south. alkaline soils. Verticillium wilt
and canker.
Maackia amurensis Full sun Adapts to a broad range High Unknown No pests or By seed
of soil types and pH. diseases are
Prefers well-drained soils. normally seen
on this tree.
Prunus sargentii Full sun Adapts to a broad range High Moderate Less susceptible By seed and
of soil types and pH. to disease than cuttings
Prefers well-drained soils. other cherries;
long-term health
usually not
MAFES Bulletin 849
affected by pests.

7. MAFES Bulletin 849 7
Northampton, MA. Its short-trunked
habit, the framework of its strongly as-
cending branches, and its mottled gray
and tan bark, all produced a unique
winter character that was enhanced by
a dusting of new snow. I returned the
following summer to find a tree with
rounded habit and dense crown, the
leaves five-lobed, each lobe tapering to a
point that is blunt at its tip. In autumn
the foliage turned to golden-yellow.
I have seen several specimens of this species since that first
encounter and they all presented the same characteristics except
for a great deal of seedling variation in growth habit. This has led
to the development of State Street® (‘Morton’), a recent selection
from the collections of The Morton Arboretum, Lisle, IL, and
introduced by the Chicagoland Grows Plant Introduction Program.
The parent tree, planted in 1929, has thrived, developing a uniform
crown with ascending branches and a broad-pyramidal habit. The
growth rate is slow to medium after establishment, 6 to 12 inches
per year.
Acer miyabei is a rare tree in New England landscapes, al-
though there is little doubt as to its hardiness. Dirr (1998) reports
it hardy to Zone 4, citing a specimen thriving at the Minnesota
Landscape Arboretum where winter temperatures drop to –30 °F.
Considered more drought tolerant than Acer platanoides (Norway
Maple), A. miyabei would make an excellent substitute for this non-
native invasive species in New England landscapes.
Acer triflorum, Three-flower Maple
Discovered in 1896 in Manchuria,
this species was introduced to the
United States in 1923. While consid-
ered an extremely desirable small
maple, difficulties with propagation
have restricted its availability. Like
Acer griseum, it is a trifoliate maple,
each leaflet with a few course teeth or
sublobes. The fall foliage color of this
maple is one of its best ornamental
features, described as brilliant red to
yellow-pink or salmon-pink, the most
beautiful of the trifoliate maples. The

8. 8 MAFES Bulletin 849
foliage of a specimen growing in Littlefield Garden (University of
Maine, Orono) turned to a brilliant orange in the past three
autumns.
Three-flower Maple produces three greenish-yellow flowers
clustered together in spring and followed by 1- to 1.5-inch-long
winged seeds that persist on the tree. The flowers are inconspicuous
and not showy while the fruits, tan at maturity, are more notice-
able.
Another highly ornamental feature of this tree is its finely scaly
bark that curls in coils to give the trunk a handsome rugged look and
accounting for an alternate common name, rough-barked maple.
This feature is particularly striking in multi-trunked trees and, in
fact, A. triflorum is routinely grown with multiple trunks or with a
single short trunk that divides within a few inches of the ground
into multiple leaders.
Typically considered a small tree, I witnessed an old tree at the
Arnold Arboretum that must be at least 60 feet tall. Most trees in
cultivation, however, seldom exceed 25 feet in height.
Cercis canadensis, Eastern Redbud
One cannot grow up in the South, as I
did, and not be aware of this small flower-
ing tree. With the flowering dogwood
(Cornus florida), it is a herald of spring. I
have fond memories of old trees growing
along the riverbank at Mulberry Planta-
tion in Charleston, SC, their leafless late
winter crowns strewn with long gray
strands of Spanish moss blowing in the
breeze. They reminded me of old men. And
the Spanish moss (not truly a moss but an epiphyte, a member of the
pineapple family) was the perfect foil for the purple-pink flowers
that covered the early spring branches before the leaves emerged.
After flowering the heart-shaped leaves emerged, dark green for
summer, then a soft yellow in autumn.
Growing in the open, C. canadensis can be a relatively large
tree, perhaps 30 feet or more in height. Most redbuds found in the
woodland understory and in managed landscapes are smaller,
typically 20 feet high. They have an irregular growth habit when
young, but assume a graceful flat-topped vase habit as they mature.
Trees usually branch very low to the ground, resulting in multi-
trunked specimens. Whether allowed to grow in this manner or
trained to a single trunk, redbuds require pruning to develop a

9. MAFES Bulletin 849 9
strong structure. Branches with narrow (“V”-
shaped) branching angles relative to the main
trunk should be completely removed in favor of
branches with a wider (“U”-shaped) angle. Also,
branches should be spaced about 6 to 10 inches
apart along the main trunk.
Redbud flower buds are not as cold hardy as
the vegetative buds and can often be damaged
by extreme cold. In the past, this has prevented
the use of redbuds in northern New England
landscapes. However, for the past five winters
I have been evaluating a promising strain of C. canadensis that was
introduced by Bailey Nurseries of Minnesota as their “Minnesota
Strain,” seedlings from a tree growing at the Minnesota Landscape
Arboretum. I learned from Ed Haselkus, Longenecker Arboretum
at University of Wisconsin, Madison, that this strain originated as
a selection from a wild population growing in Illinois. Plants
propagated from the original selection were subsequently grown
and flowered successfully at Longenecker. In the early 1990s,
Bailey Nurseries gave plants of the “Minnesota Strain” to Dr. Paul
Cappiello, my predecessor, and they were planted in the nursery at
The University of Maine, Orono. I transplanted five of these trees
to the Small Tree Evaluation Trials in May 2000.
Maackia amurensis, Amur Maackia
Maackia amurensis, the Amur Maackia, is a small, vase-shaped
and round-headed tree of considerable ornamental character. I
have photographed and studied this species throughout New En-
gland and while every arboretum and college campus seems to have
at least one Amur Maackia, I have yet to see one in a residential
landscape or along a city street! It is not a common tree in New
England.
The basis for this lack of popularity eludes me. Amur Maackia’s
mature size, 20 to 30 feet high, is ideally suited to small residential
gardens, city streets and even planters. Its shiny, dark amber, outer
bark peels into loose flakes and curls, revealing small sharp-angled
patches of inner bark. The rich color of its trunk and branches
coated in new snow will add warmth to any winter landscape.
In spring, Amur Maackia’s emerging foliage is a soft gray-green
due to pubescence on the leaves. Summer foliage, however, is a bold,
rich green. Each compound leaf is composed of five to seven leaflets,
each about 1 to 3 inches long. The one shortcoming of Amur Maackia

10. 10 MAFES Bulletin 849
is lack of good fall color, the leaflets falling as
they turn yellow-brown.
Maackia amurensis belongs to the bean
family, the Fabaceae, and is closely related to
Cladrastis kentukea or American Yellowwood
(the difference being that the leaf buds of
Maackia are solitary and not hidden by the base
of the petiole). Family ties are evident in the off-
white pea-like flowers that occur in early to
mid-July (Maine) in 4- to 6-inch-long terminal
racemes, smelling like new mown grass and typically alive with
bumblebees. The fruit is a 2- to 3-inch-long pod. While it is matur-
ing, the pod is a lighter shade of green than the foliage, providing
a very appealing contrast in color and texture. The pod matures to
brown and lingers after the leaves have dropped.
Amur Maackia also passes the test of durability. Lacking any
serious pest or disease problems, it is extremely cold hardy, growing
successfully in Zone 3. I did receive one report from New Hampshire
of serious Japanese beetle infestation on Amur Maackia. I found
this surprising, as none of the several trees I have visited in
Massachusetts or Maine have shown signs of insect feeding.
With such impressive credentials, I scratch my head and con-
tinue to wonder why Maackia amurensis is not used more fre-
quently. Could it be problems with propagation, the nemesis of
many otherwise good landscape plants? According to the experts,
Amur Maackia is easily grown from freshly collected seed that is
either soaked in hot (190 °F) water or acid scarified. In fact, several
students in The University of Maine Landscape Horticulture Pro-
gram have grown Maackia amurensis from seed collected off the
tree in Littlefield Garden. So the mystery remains.
Prunus sargentii, Sargent Cherry
This is the hardiest (Zone 4) of the
taller Japanese cherries and one of the
finest of all cherry trees. It is named for
Charles Sprague Sargent (1841–1927),
noted horticulturalist and plant hunter.
Blooming in mid-May in Orono, before
the foliage, the flowers are single, pink
to deep pink, on slender pedicels. The
bitter cherries are small (3/8 inch) and
ovoid, ripening to dark purple in summer when the birds quickly
devour them. The bark, particularly attractive in winter, is brown

11. MAFES Bulletin 849 11
to red-bronze and marked with horizontal len-
ticels. The foliage is a colorful bronze in early
spring, turning deep green during summer and
orange to red in fall.
The habit of Sargent Cherry is upright with a
rounded top. It grows rapidly to a height of 40 to 50
feet with a comparable width, casting dense shade.
The oldest specimen in America, grown from seed
sown in 1890 at the Arnold Arboretum, had to be
taken down because of storm damage. The record
tree in cultivation, growing in Puyallup, WA, is 45 feet high,
although the species will grow to 80 feet in the wild.
Sargent Cherry makes an excellent street tree in areas that can
accommodate its spreading canopy. No other cherry is as stress
tolerant. It can also be used in the tree lawn area between the curb
and sidewalk or as a specimen tree in the lawn. During its relative
short life expectancy, about 20 years, it will grace any landscape
with beauty throughout the year.
EVALUATION METHODS
Cultural Methods
Table 3 presents information on sources and planting dates for
each of the five species. For Maackia amurensis both the variety
buergeri and a cultivar, ‘Starburst’ were evaluated. For Prunus
sargentii, the white-flowering cultivar ‘Princeton Snowcloud’ was
evaluated. Both the M. amurensis ‘Starburst’ and the P. sargentii
‘Princeton Snowcloud’ were planted bareroot as received from the
supplier. The C. canadensis was transplanted from a holding
nursery adjacent to the trial plots. All other trees were planted from
containers.
Five trees of each species and cultivar were planted in a full sun
research plot at the Lyle E. Littlefield Ornamentals Trial Garden
(Orono, Maine) using standard landscape installation practices.
Each tree was randomly assigned to one of 98 available planting
locations in a completely randomized block experimental design.
Trees were planted in rows spaced 4.6 meters (15 feet) apart with
3 meters (10 feet) between trees in each row. Soil tests on five
separate samples collected across the planting area indicated a
sandy loam soil ranging in pH from 5.7 to 6.0. Organic matter
ranged from 6.8% to 8.0% while levels of P, K, Ca, and Mg all ranged
from medium to optimum. No soil amendments were added to the
backfill at planting and no fertilizer was applied throughout the
study. All trees were watered weekly, as needed to supplement

12. 12 MAFES Bulletin 849
Table 3. Sources and planting dates for the five species of small
flowering trees.
Planting
Botanical Name Source Date
Acer miyabei Heritage Seedlings (Salem, OR) May 1999
Acer triflorum Heritage Seedlings (Salem, OR) May 1999
Cercis canadensis
“Minnesota Strain” Bailey Nursery(St. Paul, MN) May 2000
Maackia amurensis Seed from tree in Littlefield June 2000
var. buergeri Garden, Univ. of Maine, Orono
Maackia amurensis Princeton Nursery(Princeton, NJ) May 2000
‘Starburst’
Prunus sargentii Princeton Nursery (Princeton, NJ) May 2000
‘Princeton Snowcloud’
rainfall, during the first year to ensure successful establishment; in
subsequent years, no irrigation was used to supplement rainfall.
Trees were monitored for insect and disease problems, but no
chemical controls were applied. Pruning, including removal of
dead, damaged, diseased, and crowded branches, was conducted in
the second and subsequent years to develop scaffold branching
systems and maintain tree health.
Measurements of Tree Growth
Plant height was measured immediately after planting and on
June 1, 2003. Plant width at the widest point and trunk diameter
15 centimeters from the ground was also measured on June 1, 2003.
The C. canadensis were received from the supplier and planted
prior to the start of this study and there were no records of initial
tree height.
Climate Data
Temperature and rainfall data were obtained from Maine State
Climate Office records for Bangor, Maine.

13. MAFES Bulletin 849 13
RESULTS
Table 4 presents winter temperature and monthly precipita-
tion data for Bangor, ME, located approximately six miles from the
evaluation site. Lowest annual minimum temperatures for the four
winters of this study ranged from –12 °F (-24 °C, 2002) to –22 °F (-
30 °C, 2000). A plant hardiness zone map for Maine, based on
average annual minimum temperature data for the period 1974 to
1986 (Lois Berg-Stack, University of Maine Cooperative Extension
Bulletin #2242), positions the Bangor-Orono area in USDA Hardi-
ness Zone 5a. The average annual minimum temperature for the
four-year period of this study was –18 °F (-28 °C), consistent with
this Zone 5a ranking.
The period of this study, May 1999 to March 2003, was below
average in total precipitation. The second year of the study, 2001,
was the driest year on record (15.61 inches below normal), while
August 2002 and January 2003 were the driest and third driest
months on record, respectively. For the growing seasons (April
through September) of 2000, 2001 and 2002, rainfall amounts were
below normal. During the growing season of 2001, total precipita-
tion was 65% of the 30-year mean.
Table 5 shows changes in tree height during the study period as
well as measurements of tree width and trunk caliper at the end of
the study period. Mean growth rates were calculated from the
differences in mean tree height. Tree size at planting for the C.
canadensis was unknown and thus a growth rate for this species
could not be determined. Most trees, including all A. triflorum and
P. sargentii ‘Princeton Snowcloud’, survived and grew during the
study period. One tree each for the remaining three species and M.
amurensis var. buergeri did not survive. One C. canadensis did not
survive transplanting from the nursery and was removed on June
6, 2000. An errant vehicle destroyed a M. amurensis ‘Starburst’.
Reasons for the other losses were not obvious.
Prunus sargentii ‘Princeton Snowcloud’ lived up to its reputa-
tion as a fast-growing tree, averaging 75 centimeters (30 inches)
increase in height per year. While Maackia are considered slow-
growing trees, the M. amurensis ‘Starburst’ averaged an increase in
height of 51 centimeters (20 inches) per year in this study, second
only in growth rate to P. sargentii ‘Princeton Snowcloud’. The M.
amurensis var. buergeri, however, averaged only 12 centimeters (5
inches) increase in height per year. The two maples were compa-
rable in growth rate during the study period with A. miyabei
showing a slightly higher rate of growth (Table 5). This difference
was due to one exceptional A. miyabei tree (#4 in Table 5) that had

14. 14 MAFES Bulletin 849
Table 4. Lowest minimum winter temperatures (LowTMin, °F),
monthly precipitation amounts (Prcp, inches), annual
precipitation totals, and growing season (April –
September) precipitation totals for the period January
2000 until March 2003. For comparison, 30-year
precipitation means are included.
Prcp
Year Month LowTMin Prcp (30-yr. Mean)
2000 January -22 3.82 3.34
February -18 2.36 2.54
March 2 3.71 3.44
April 5.63 3.32
May 4.24 3.40
June 2.63 3.41
July 2.08 3.24
August 2.03 2.99
September 1.35 3.39
October 3.28 3.46
November 2.83 3.69
December -2 3.75 3.33
Annual Total 37.71 39.57
Growing Season Total 17.96 19.75
2001 January -13 1.51 3.34
February -9 1.87 2.54
March -16 2.84 3.44
April 0.77 3.32
May 1.51 3.40
June 1.54 3.41
July 3.18 3.24
August 1.72 2.99
September 4.04 3.39
October 1.22 3.46
November 1.93 3.69
December 2 1.83 3.33
Annual Mean 23.96 39.57
Growing Season Mean 12.76 19.75
2002 January -6 3.35 3.34
February -12 3.43 2.54
March 11 3.33 3.44
April 5.68 3.32
May 2.51 3.40
June 3.56 3.41
July 2.24 3.24
August 0.73 2.99

15. MAFES Bulletin 849 15
Table 4. Continued.
Prcp
Year Month LowTMin Prcp (30-yr. Mean)
2002 September 4.19 3.39
October 3.19 3.46
November 4.64 3.69
December -2 3.94 3.33
Annual Mean 40.79 39.57
Growing Season Mean 18.91 19.75
2003 January -17 0.94 3.34
February -21 2.65 2.54
March -10 4.08 3.44
an individual growth rate much higher than the species mean. This
same tree developed a trunk caliper twice as large as the other A.
miyabei.
An infestation of Japanese beetles on P. sargentii ‘Princeton
Snowcloud’ was the only serious pest problem during the course of
this study, occurring in the summer of 2000. All five trees were
affected, each losing most of the foliage. The leaves were replaced
in late August, however, and the trees survived the following winter
without dieback. Japanese beetles were not a problem on these
trees in subsequent years.
During the extreme drought of summer 2001, the foliage of M.
amurensis var. buergeri turned brown in mid-summer and all trees
were defoliated by August. This early leaf loss did not affect
subsequent winter survival, but it may have affected mean growth
rates for the study period. The larger M. amurensis ‘Starburst’ did
not experience this problem.
CONCLUSIONS
The five tree species described in this study have proven to be
winter hardy in the Bangor-Orono area (Zone 5a), drought tolerant
and relatively pest free, three factors that recommend them for
increased use in Maine landscapes. Over the four years of this
study, the trees were exposed to winter temperatures as low as –22
°F, as well as desiccating winter winds, without apparent damage
to overwintering buds.

16. 16
Table 5. Measurements of tree height at planting and measurements of tree height, width and trunk caliper on June
1, 2003. Measurements in cm (inches). A (*) indicates that the tree did not survive.
Tree Tree Mean Tree Width (at Trunk caliper (at
Tree Height Height on Growth Rate widest point) on 15 cm above the
Botanical Name Number at planting June 1, 2003 cm (in)/year 6/1/2003 ground) on 6/1/2003
Acer miyabei 1 41 (16) 94 (37) 13 (5) 41 (16) 1.3 (0.5)
2 46 (18) 216 (85) 43 (17) 91 (36) 1.9 (0.8)
3 35 (14) 61 (24) 7 (3) 58 (23) 1.9 (0.8)
4 62 (24) 284 (112) 56 (22) 56 (22) 3.8 (1.5)
5 33 (13) * * * *
Mean (n=4) 43 (17) 164 (65) 30 (12) 62 (24) 2.2 (2.0)
Acer triflorum 1 80 (31) 178 (70) 25 (10) 89 (35) 1.9 (0.8)
2 91 (36) 142 (56) 13 (5) 91 (36) 1.9 (0.8)
3 70 (28) 168 (66) 25 (10) 61 (24) 2.5 (1.0)
4 82 (32) 185 (73) 26 (10) 51 (20) 1.9 (0.8)
5 79 (31) 213 (84) 34 (13) 91 (36) 2.5 (1.0)
Mean (n=5) 80 (32) 177 (70) 24 (10) 77 (30) 2.1 (0.9)
Cercis canadensis
“Minnesota Strain” 1 Not known 241 (95) - 183 (72) 3.2 (1.3)
2 “ 291 (115) - 244 (96) 6.4 (2.5)
3 “ 309 (122) - 247 (97) 5 (2.0)
4 “ 276 (109) - 221 (87) 4.4 (1.7)
5 “ * - * *
Mean (n=4) 279 (110) 224 (88) 4.8 (1.9)
MAFES Bulletin 849

17. Table 5. Continued.
Tree Tree Mean Tree Width (at Trunk caliper (at
Tree Height Height on Growth Rate widest point) on 15 cm above the
Botanical Name Number at planting June 1, 2003 cm (in)/year 6/1/2003 ground) on 6/1/2003
Maackia amurensis
MAFES Bulletin 849
var. buergeri 1 19 (7) 51 (20) 11 (4) 15 (6) 1.0 (0.4)
2 21 (8) 61 (24) 13 (5) 25 (10) 1.0 (0.4)
3 25 (10) 58 (23) 11 (4) 20 (8) 1.3 (0.5)
4 26 (10) * * * *
5 29 (11) 64 (25) 15 (6) 15 (6) 1.0 (0.4)
Mean (n=4) 24 (9) 59 (23) 12 (5) 19 (8) 1.1 (0.4)
Maackia amurensis
‘Starburst’ 1 140 (55) 311 (122) 57 (22) 118 (46) 3.2 (1.3)
2 135 (53) 281 (111) 49 (19) 115 (45) 3.8 (1.5)
3 130 (51) * * * *
4 145 (57) 314 (124) 56 (22) 122 (48) 3.8 (1.5)
5 135 (53) 259 (102) 41 (16) 102 (40) 3.8 (1.5)
Mean (n=4) 139 (55) 291 (115) 51 (20) 114 (45) 3.7 (1.5)
Prunus sargentii
‘Princeton Snowcloud’ 1 106 (42) 352 (139) 82 (32) not measured 5.1 (2.0)
2 195 (77) 344 (135) 50 (19) “ 5.1 (2.0)
3 90 (35) 375 (148) 95 (38) “ 5.1 (2.0)
4 97 (38) 309 (122) 71 (28) “ 5.1 (2.0)
5 120 (47) 359 (141) 75 (30) “ 5.1 (2.0)
Mean (n=5) 122 (48) 348 (137) 75 (30) * 5.1 (2.0)
17

18. 18 MAFES Bulletin 849
Of particular importance to Maine growers and landscapers is
the flower bud winter hardiness of the Cercis canadensis strain
used in this study. Of the original twenty or more plants of this
strain given to Dr. Cappiello by Bailey Nurseries, the five trees in
this study represent the hardiest of the group, flowering above the
snow line each year of the study. In addition to these five trees, there
are three trees from the same Bailey shipment that were trans-
planted to the ornamentals display area of Littlefield Garden in
May 2000. These three trees have also flowered consistently above
the snow line each year. These eight trees were propagated from
seed collected from a single tree growing at the Minnesota Land-
scape Arboretum, indicating that their superior winter hardiness is
a trait that can be sustained through seed propagation. The “Min-
nesota Strain” continues to be available from Bailey Nurseries;
however, I believe it is time to start collecting seed from the trees
in this study and propagating an “Orono Strain”.
The summer droughts of the past few years have increased
interest in drought-tolerant trees for Maine landscapes. The five
species recommended by this study survived the driest summer on
record (2001) without supplemental irrigation. Although all of the
growing seasons after planting were below normal in precipitation,
these trees not only survived, they thrived. The drought tolerance
of Prunus sargentii, as evidenced by the performance of ‘Princeton
Snowcloud’ in this study, is also evident in the performance of
several trees of the species on The University of Maine Orono
campus. Similarly, the Maackia amurensis var. buergeri from
which seed was collected to propagate the trees used in this study
has continued to flourish in Littlefield Garden during the recent
drought, as has a single specimen of Acer triflorum.
I have yet to encounter either of the two maples of this study, A.
triflorum and A. miyabei, in a Maine landscape. Both are readily
available, so I have to conclude that they are simply in need of
greater recognition as attractive, winter-hardy and drought-toler-
ant landscape trees. Based on the results of this study, landscape
designers should be encouraged to use these two maples.
None of the tree species in this study are native to Maine and
only one, C. canadensis, is native to North America. In recommend-
ing non-native trees for use in managed landscapes, the invasive
potential of each species should be evaluated in order to avoid the
use of non-native invasive tree species such as Norway Maple (Acer
platanoides) that escape from cultivation and threaten the integ-
rity of natural areas. At this time the five tree species recommended
by this study show no invasive potential. For example, A. miyabei

19. MAFES Bulletin 849 19
has been under observation at The Morton Arboretum since 1929
without any indication of invasive potential. This fact, along with
the demonstrated drought tolerance of Miyabe Maple, makes it an
excellent replacement for Norway Maple in future landscapes.
LITERATURE CITED
Dirr, M.A. 1998. Manual of Woody Landscape Plants. Stipes
Publishing, Champaign, IL.